Such a device operates as a peripheral device in dependence on a control device. The two devices are interconnected by a multicore capable through which data are transmitted universally and serially, referred to as Universal Serial Bus or USB for short. The control device has a power supply part and is accordingly capable also of supplying the peripheral device with current via the multicore cable. The power supply part has a given output voltage and is capable of delivering a maximum output current level, i.e. the current is limited as to its strength. If a peripheral device is supplied with power through the cable and if it exhibits a fluctuating current consumption, then the average current consumption will be lower than the maximum possible current consumption. Consequently, the maximum possible power made available by the power supply part is not fully utilized.
It is an object of the invention to increase the average power consumption of a peripheral device supplied with current by the energy supply part without exceeding the maximum admissible current level.
According to the invention, a capacitor is connected to the input of the device. The principle is that energy is put into intermediate storage in the capacitor during those time periods in which the peripheral device requires less than the maximum possible power. The power of the peripheral device can be increased in this manner.
Advantageously, a DC-DC converter is connected upstream of the storage capacitor. The DC-DC converter converts the voltage V1 applied to the supply connection to a higher voltage V2. Whenever the consumption of the peripheral device exceeds the maximum possible power level, the storage capacitor will make good the deficit. The voltage at the storage capacitor will drop. The moment the consumption of the peripheral device drops and the supply connection makes more electric power available than is required by the peripheral device, the DC-DC converter will branch off the excess energy into the capacitor. The storage capacitor is charged again until the higher voltage V2 is achieved. By this method, current consumption peaks of the peripheral device can be higher than the maximum possible power level, while the maximum possible power made available by the power supply will never exceed the maximum. Peripheral devices which usually operate at higher voltage levels can now be used because of the higher voltage values.
Advantageously, a current limiter is connected to the input. If more power is used than the power supply part is capable of delivering, the power supply part could become damaged by an overload, or it may be switched off by a safety cut-out mechanism. The current limiter at the input of the DC-DC converter limits the input current and prevents damage to the power supply part or triggering of the cut-out mechanism.